Balanced Audio Technology REX II User manual

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REX II
WARRANTY REGISTRATION FORM
Unit Serial Number:
_______________________________________
Customer Name:
_______________________________________
Address:
_______________________________________
_______________________________________
Date of Purchase:
_______________________________________
Purchased From:
Dealer Name:
_______________________________________
Address:
_______________________________________
_______________________________________
IMPORTANT NOTE:
In order to receive the full five year product warranty, please mail
this completed form together with a copy of your sales receipt to

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Balanced Audio Technology at the address below, within thirty days
of purchase.
Failure to do so will result in the product being warrantied for one
year from the date of manufacture.
1300 First Stat Blvd. Suite A Wilmington DE 19804 Tel: [phone] Fax: [phone]

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REX II
Vacuum Tube
Balanced Stereo Preamplifier
Owner's Manual
1300 First Stat Blvd. Suite A Wilmington DE 19804 Tel: [phone] Fax: [phone]

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TABLE OF CONTENT
CURRENT SOURCES 4
CHANGING CURRENT SOURCES 5
AC SHUNT VOLTAGE REGULATORS 6
INTRODUCTION 7
Package Content 7
Physical Placement 8
Configuring the REX II 8
Connecting to your system 9
FRONT PANEL CONTROLS 10
REX II Power On sequence 10
Turning the REX II Off 108
PHASE Button and LED 11
MONO button and LED 11
MUTE button and LED 11
INPUT selection 11
VOLUME knob 11
DISPLAY format 12
FUCTION button 12
DISPLAY Brightness function 13
MUTE function 13
REX II PROGRAMMABLE FUNCTIONS 14
Parameter Definitions 15
PROGRAMMING THE REX II 15
BALANCE adjustment 15
VOLUME offsets 16
PHASE 17
MONO/STEREO 17
MAXIMUM gain 17
FIXED gain 18
DISPLAY MODE 18
INPUT NAME 19
REMOTE CONTROL FUNCTIONS 20
Volume Up/Down 20
Mute 20
Fade 20
Input 20
Display/Power 21
Fuse Protection 21
Servicing 21
Cleaning 21
RESETTING THE REX II 22
WARRANTY 23
Vacuum Tube Current Sources in REX II
Your REX II incorporates a unique feature that allows you to optimize its sound to tailor it to your
individual taste or system requirements.
The Vacuum Tube current sources incorporated in the REX II, being part of the signal gain stage, have a
direct effect on the unit’s sound. Changing the tube type used in that circuit allows the user an extra
degree of control over the sound of the unit.

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In its standard configuration the REX II current sources use the Russian 6C19 tubes. That tube is
basically a miniature version of the famous 6C33 tube, and provides, in our view, the best combination
of sonic characteristics and electrical performance.
However, the unique design of the REX II allows you to also use other tube types in that application.
Currently, the user has the following three choices for vacuum tube Current Sources:
1. The standard 6C19 tube current source as installed from the factory.
2. The 6H30 SuperTube current source which requires the purchase of the X-PAK accessory.
3. The 5881 tube current source.
NOTE: There are TWO Current Sources in REX II, located in the Power Module.
The REX II X-PAK accessory includes two current source boards.
In order to change the tube type the user needs to remove the installed Current Source boards, and replace
them with either another type, designed for a particular tube type, or install the 5881 tubes as a direct plug-in.
Only the 5881 tubes can be used directly upon the removal of the 6C19 current source board.

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Please consult the factory regarding options for other tube types that may be available in the future.
WARNING:
The following procedure should only be performed by qualified personnel
To change the current source:
1. Turn the unit OFF and wait at least 5 minutes to allow the tubes to cool down and the power
supply charge to dissipate. Remove the Power Module top cover.
2. Remove the six screws holding each current source board.
3. Pull the current source boards straight up to disengage its connectors.
4. Install the new current source boards making sure their connectors are properly aligned. Boards
will be positioned properly when the mounting holes in the circuit boards align with the standoffs.
5. Install the six mounting screws.
6. Turn the unit ON.
AC SHUNT VOLTAGE REGULATORS
The REX II preamplifier incorporates another feature that allows the user to optimize its sound – the
AC Shunt voltage regulators.
The AC Shunt voltage regulators perform the final “cleaning” of the REX II power supply rails.
They work to reduce the minute fluctuations in the DC voltages that may degrade the sound.
The AC Shunt Voltage Regulators are located in the REX II Power Module.

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They incorporate two types of vacuum tubes, user selectable for the desired sound: 6C45 and 6H30.
To change the AC Shunt tube type remove the Power Module top cover and move the board-mounted
switch S1 to desired position. The switch is located close to the center of the board.
Only the selected tubes will have their filaments running at any time.
INTRODUCTION
Thank you for your purchase of the Balanced Audio Technology REX II
preamplifier. Please read this owner's manual to obtain the full benefit of the REX II
in your system. It will provide you with the needed safety information and
operating procedures for this exceptional unit.

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WARNINGS:
To prevent the possibility of serious injury, electrical shock or fire:
DO NOT operate with the cover removed.
DO NOT expose to rain or moisture.
DO NOT defeat the ground power-plug.
DO NOT replace fuse with anything other than the same type and rating as supplied
by the factory.
Package Contents
Included in the box set should be the following:
Description Quantity
REX II Control Module 1
REX II Power Module 1
Power Cord 2
Spare Fuse 2
Torx Wrench (T-15) 1
Spare Top Cover Screws 1 10
User’s Manual 1
VK-R3 Remote Control (If ordered)
Save all the packaging material in a safe dry area for the unlikely event that
you need to return the REX II to the factory for service.
PHYSICAL PLACEMENT
It is recommended that you provide at least 6" of free space around each module
comprising the REX II preamlifier for proper ventilation.
Mount the modules on a hard surface with proper ventilation underneath.
Do not stack the REX II preamplifier on top of other units, nor vice versa.
WARNING

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Stacking the modules (putting the Control Module on top of
the Power Module) is NOT permitted.
CONFIGURING THE REX II PREAMPLIFIER SYSTEM
The REX II preamplifier system consists of two modules.
Control Module performs all the control functions associated with the
duties of the preamplifier in your system. It also receives and processes the
remote control commands.
Power Module works in conjunction with the Control Module as an outboard
power supply.
The two modules are connected by two detachable cables. In addition each module
has its own power cord that must be plugged into the power outlet.
WARNING
Make sure your REX II is powered DOWN before making or
changing ANY connections between its two modules, to the
source components or power amplifiers.
Connect the two detachable cables between the modules, making sure the channels
are connected properly.
Plug the two power cords into power receptacles.
Make all the signal connections.
CONNECTING THE REX II TO YOUR SYSTEM
Balanced Components
Use balanced XLR interconnects. All input and output connectors are clearly
marked on the back panel.
Note: The REX II XLR connectors are wired as follows:

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Pin 1: common/shield
Pin 2: positive
Pin 3: negative
For the REX II, use the Main 1 XLR Output for connection to your balanced power
amplifier. The Output 2 is configured as an RCA connector output.
Single-Ended Components
Single-ended components have RCA connectors. The REX II preamplifier is
designed to work with balanced interconnects only. If single ended components
need to be connected to the preamplifer, then the RCA/XLR adapters should be
used. These adapters are available from an authorized Balanced Audio Technology
dealer at a nominal charge.
Two types of adapters are available:
Input Adapters: RCA Female to XLR Male
Output Adapters: RCA Female to XLR Female.
REX II FRONT PANEL CONTROLS
STANDBY Button and LED
The Standby button is used to turn the unit ON and OFF and to switch the
preamplifier into its Standby mode. The LED indicates the status of the unit’s
power circuitry and has four state:
LED OFF Display OFF Unit is in OFF state
Display ON Unit is in ON state

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LED Flashing Unit is going through its Power-ON routine
LED ON Unit is in its STANDBY mode
When the unit is plugged into a power line, it will stay in the OFF state until the
Standby button is pushed. The LED will then start blinking and the unit will go
through a 50second warm-up sequence. At the end of that sequence it will turn
ON.
Pressing the button again will switch the unit into its Standby mode.
The REX II can be turned OFF by pressing and holding the Standby button.
REX II Power-On sequence:
When you turn the REX II On, it will automatically go through a gentle power-on
sequence. This sequence takes 50 seconds, during which time the display and the
Standby LED will be flashing, indicating the status of the unit.
In addition, the blue LED on the Power Module front panel will also light.
1. The number on the display during this time indicates the volume setting. This
will usually start at 000. This setting can be changed during this time by
using the volume knob or Volume Up/Down buttons on your VK-R3 remote
control transmitter. In addition, such functions as Phase, Mono, input
selection and Mute can be changed during this time either from front panel or
through the remote control.
2. Normally the REX II will be not muted (Mute LED on the display is OFF) and
will begin playing at the end of the 50 second delay. If so desired, the unit
can be put in the MUTE mode during this delay interval either by depressing
the front panel MUTE switch or by using the MUTE button on the VK-R3
remote control transmitter.
Turning the REX II Off:
The unit can be turned OFF by pressing and holding the Standby button. It will
automatically mute.
PHASE button and LED
This button allows the user to invert the absolute polarity of the signal to
compensate for some recordings that are made out-of-phase. The LED indicates
whether the unit is in its INVERTING or NONINVERTING mode. This function is also
accessible via the VK-R3 remote control.
LED OFF Non Inverting operation

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LED ON Inverting operation
MONO Button and LED
The Mono button allows the user to switch the REX II in Mono operation when the
two channels are summed together. This may be useful, for example, while listening
to old monophonic recordings. This function is also accessible via the VK-R3 remote
control.
LED OFF Stereo operation
LED ON Mono operation
MUTE Button and LED
The Mute button disables the preamplifier output. It is recommended that the Mute
be engaged any time the signal cables are changed or any other system
configuration changes are being made. This function is also accessible via the VK-R3
remote control.
LED OFF Unit in Play mode
LED ON Output Muted
INPUT selection buttons 1through 5
These allow the user to select any of five available inputs to be played. The
selected input number together with its name will be indicated on the unit front
panel display as well. This function is also accessible via the VK-R3 remote control.
VOLUME Knob
This knob performs different function depending upon the unit’s mode of operation.
In normal mode it works as volume control knob.
It is also used as a data input device in various Function modes to program the unit.
For example, it is used to set the BALANCE adjustment when the REX II is switched
into its Balance mode. More on that in the corresponding sections of this manual.
The volume control knob on the REX II is linked to a digital encoder and is of a
continuously rotating type (there are no stops).
DISPLAY FORMAT:
The REX II Vacuum Fluorescent Display (VFD) is capable of showing up to twelve
alphanumeric characters. Its format depends on the mode of operation. In the
normal PLAY mode the display has the following format:
1. One character indicating the selected input number.

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2. Four-character input name. That name is fully programmable (See the
programming functions) and can include up to four character from the Latin,
Cyrillic or Greek alphabets or digits.
3. Balance adjustment indicator. Characters L or R indicate that the balance is
shifted in the corresponding direction. A BLANK character means that the
gains of both channels are identical.
4. Volume setting - three digits with the full range of 000 to 140 (See
programming section on Maximum Volume Setting)
FUNCTION Button
This button puts the unit in its programming mode. In addition to its normal PLAY
mode, there are eight programmable functions in the REX II:
BALANCE Adjustment
RELATIVE VOLUME setting
PHASE setting
MONO/STEREO setting
MAXIMUM volume setting
FIXED volume setting
DISPLAY (Volume) mode
INPUT NAME assignment
Pressing this button while in PLAY mode will switch the unit into programming
mode. Once in the programming mode, pressing the Function button will switch the
unit into its NEXT programmable functions. The unit will stay in the programming
mode until the exit command is issued. To EXIT the programming mode at any
time, press and hold the Function button for about TWO seconds.
DISPLAY Brightness Function
Changing the Display Brightness: The REX II display can be dimmed or
turned completely OFF by simply pressing the DISPLAY button on your VK-R3
remote control transmitter.
Each press will reduce the brightness of display and LED indicators in steps
from full ON to OFF, and then one press back to full ON. The LED indicators

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will dim but never turn completely OFF. With the display OFF, issuing any
remote control command that would normally require a display change (i.e.:
Volume, Input selection, Fade) will automatically turn the display back ON.
MUTE Function:
The REX II has two mute modes: manual and automatic. The blue LED above the
Mute button goes ON when the unit is in MUTE state. To MUTE the REX II, depress
the MUTE button located on the right side of the front panel. Depressing this
button again will return the unit to its normal operation and turn the mute LED off.
When the unit is powered up it automatically self-mutes until the proper operating
points of the circuitry are reached. It will then automatically go into Play mode,
provided the Mute function was not activated (the blue Mute LED is Off).
Turning the REX II OFF even for short time, will make the unit reset its power
sequencing circuit and mute its output. It will then require 50 seconds for the unit
to become operational again.
REX II PROGRAMABLE FUNCTIONS
The REX II programming functions allow the user to optimize the unit configuration
for any particular system set up. The flexible programming facility defines each
signal input with a group of user-selectable parameters that are then stored in the
unit’s memory. Every time a particular input is selected, its unique combination of
parameters is loaded into the operating memory. Programming is easy and is
accomplished through using just two front panel controls -: the Function button

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and Volume knob, or corresponding remote control buttons (Function and Volume
Up/Down buttons).
Every unit comes from the factory with a default set of parameters stored in its
memory. This set of parameters is usable for many applications. The default set
includes the following parameters:
BALANCE ZERO
RELATIVE VOLUME ZERO
PHASE Non-Inverting
MONO/STEREO STEREO
MAXIMUM VOLUME 140
FIXED GAIN OFF
DISPLAY COUNTS
INPUT NAMES 1 TAPE
2 TUN
3 CD1
4 AUX1
5 AUX2 or PH1 if the phono card is
installed
The user may at any time, configure the unit to a particular set of system
requirements. For example, input names can be changed to reflect a given
system’s source configuration.
Parameter Definitions:
Every input of the REX II is defined with the following set of parameters.

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1. Input name (Examples include CD1, DVD1, PH-1, VKD5, or any other
combination of up to four characters including the Latin, Cyrillic and Greek
alphabet as well as digits)
2. Balance adjustment – gain shifted Left or Right.
3. Volume offset relative to any other input (to compensate for gross
differences in various sources levels)
4. Phase: Inverting, Non-inverting or Last configuration
5. Stereo, Mono or Last configuration
6. Maximum allowable volume setting for a particular input. This is a convenient
safety feature in some instances.
7. Display mode. This allows the user to switch the volume display to operate in
any of the three modes: relative Counts, DBU (Decibels referenced to Unity
gain) or DBM (Decibels referenced to Maximum gain).
8. Fixed volume mode: this allows any input to be set with a preferred fixed
volume setting, and is usable, for example, in Audio/Video installations.
With this flexibility it is possible, for example, to set the CD input to be Stereo and
Non-Inverting, while the Phono input would be Mono and Inverting.
PROGRAMMING THE REX II
NOTE: It is important to note here that all the functions described
below are accessible either through the front panel controls or via the
VK-R3 remote control. Therefore, functions like BALANCE, PHASE,
MONO, etc. all can be performed by using the Function button on the
remote control in conjunction with the Volume Up/Down buttons.
BALANCE Adjustment.
Pressing the Function button once will invoke the Balance adjustment mode. When
in this mode, turn the volume control knob (or press the Volume Up/Down buttons
on the VK-R3 remote control) to set the balance to the desired position. An L or R
character will appear indicating that the balance is now shifted in the corresponding
direction.
Exiting the programming mode by pressing and holding the Function button
will store this adjustment for the selected input.
The BALANCE adjustment for each selected input is also stored when switching to
another input while still in the BALANCE programming mode.
RELATIVE Volume adjustment.

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It is quite common to have sources with very different output levels connected to a
preamplifier. In this case, switching between different inputs is usually
accomplished by a large change in volume. The REX II allows the user to avoid this
inconvenience by setting volume offsets between different inputs (using ANY input
as a reference).
To program this feature:
1. Select any input that you would like to use as a reference. Play music at the
level you find comfortable.
2. Press the Function button twice. The display will read: VOL 000
3. Switch to a different input. Adjust the volume while playing the music to the
level that is comparable to the reference input level. The display will indicate
the volume offset number. That number can be either positive or negative,
depending upon whether the new selected input is stronger or weaker than
the reference input.
4. Exit the programming mode by pressing and holding the Function
button or by switching to a different input.
Any input volume offset can be programmed at ANY time with respect to ANY
other input.
EXAMPLE:
The CD1 input is used as the reference. Let’s presume that the PH1 input (the
weaker source) is then programmed to play at 20 counts higher. Its volume offset
will then read 20.
The user can later select the PH1 input and using it as the reference, program the
AUX1 input to be 10 counts lower than the PH1 input. Effectively, the volume
offset from the CD1 input to the AUX1 will now become 10.
The user then can at any time verify his volume offset programming by switching
the unit in its VOLUME mode (by pressing the Function button twice) and then
selecting the inputs 3, 4 and 5. The volume offset numbers for these inputs should
then read 0, 10 and 20 respectfully. That means that the AUX1 source will be
played at 10 counts above the CD1 input and the PH1 input at 20 counts above
the CD1 input.
Alternatively, the volume offset number can be entered directly, based on your
judgement of volume difference between the two sources. To do that, select the
input, enter the VOLUME programming mode by pressing the Function button twice,
and use the volume knob to set the volume offset number that you deem desirable.
Then exit the programming mode by pressing and holding the Function
Button .
NOTE: A negative number for the selected input indicates that its gain
will be set lower than the gain of the reference input.

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PHASE programming.
Select the desired input.
Press the Function button three times. The display will read: PHASE NINV.
Use the volume knob to set the condition to NINV, INV or LAST.
Exit the programming mode by pressing and holding the Function
button .
NOTE: In the LAST mode, the state of the PHASE switch will be the
same as used the last time for that particular input.
MONO/STEREO programming.
Select the desired input.
Press the Function button four times. The display will read: STEREO
Use the volume knob to set the condition to STEREO, MONO or LAST.
Exit the programming mode by pressing and holding the Function
button .
NOTE: In the LAST mode, the state of the Phase switch will be the
same as used the last time for that particular input.
MAXIMUM gain programming
It may be desirable to limit the allowable volume setting on a particular input. To
do this:
Select the desired input
Enter the MAXIMUM programming mode by pressing the Function button five
times.
Set the display to any desired number that will now represent the maximum
allowable volume setting for the selected input.
Exit the programming mode by pressing and holding the Function
button .

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FIXED Gain mode
In some systems (some A/V installations, for example) it is desirable to set a
particular input to a fixed gain, that is then becomes unaffected by the volume
knob. Most often it is required to set the preamplifier gain to Unity (Gain of 1).
The REX II allows the user to do so by using its FIXED gain function.
Press the Function button six times.
The display will read: FIX OFF
Enter any desired number for the fixed gain on the selected input (see
below).
UNITY gain for the REX II preamplifier correspond to the following
volume setting:
CNTS display mode 100 Counts
DBU 00.0dB
DBM -20.0dB
Exit the programming mode by pressing and holding the Function
button.
DISPLAY MODE programming
The volume display of the REX II can be switched to work in any of the following
three modes:
CNTS: Relative volume counts with the range of 000 to 140
DBU: Decibel readings with respect to unity gain (0dB).
DBM: Decibel readings with respect to maximum gain (20dB)
NOTE: To avoid possible confusion, the SAME display mode setting
applies to ALL inputs. It is not possible, for example, to set one input
to CNTS and another to DBU.

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INPUT NAME programming:
The REX II allows the user to assign any a custom name to any input. Those names
may include up to four characters. The default names for the inputs are as follows:
1 TAPE
2 TUN
3 CD!
4 AUX1
5 AUX2 (It will automatically switch to PH1 if the optional phono card is
installed)
Any combination of up to four Latin, Cyrillic, Greek alphabet characters or digits can
be used to name the source. The examples may include:
CD-2, DVD1, JOHN, VKD5, MARY, BOB1, etc.
To program the input name, do the following:
Select the desired input
Press the Function button eight times. The first character of the input name will
start blinking
Use the volume control knob or the remote control Volume Up/Down buttons to
select the desired character. The characters are organized in the following
order: the digits, the Latin alphabet, the Cyrillic (Russian) alphabet, the Greek
alphabet.
Advance to the next character by pressing the Function button once.
Exit the programming mode by pressing and holding the Function button .